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Question on installing US 110v sockets in the UK.

James Doolin

I have been asked to install 110v US NEMA style sockets for a company in the UK who test equipment bound for the US before shipping. To be clear they only require a single phase 110v to 0v supply feeding 15 amp socket outlets and not the split phase 110v 110v system providing 240v from 2 legs. The machines definitely require a 60Hz supply. They have sourced a static frequency and voltage converter (Sinalda FCL-30H-3:S10-SR50 30kVa) which will take a 63 amp 3 phase 4 wire 50Hz supply and convert it to a 230v 60Hz single phase 2 wire supply. This would supply a 3 phase distribution board with single phase link kit and be populated with RCBOs to feed 10 radial circuits feeding a single 15 amp socket per circuit. I have found a board and RCBOs from Schneider which are suitable for 110v 60Hz.
My 2 main questions are - do the RCBOs need to be double pole. They have an existing 110v US style installation using double pole RCBOs, I realise these are required on reduced low voltage 55v-0v-55v installations but don't understand why they would be required in this instance. My second question is regarding the earthing on the secondary side of the voltage frequency converter. The neutral of the secondary side of the converter is referenced to earth as standard. I would like to satisfy myself that this is safe as this is introducing a neutral earth link beyond the incoming supply.
I have realised that there is an issue with the converter the client has specified as it's output is variable so will be asking if it can be replaced for a fixed output model.
I also realise that it is unclear whose regulations I would be working to. I have spoken to my governing body and have been told that although BS7671 wouldn't cover such an installation, if it was installed in line with US regulations they can't see a problem with it. To this end I have found out as much as I can about the US system but realise the limitations of learning from Youtube!
Would appreciate any advice offered as I am a little out of my comfort zone.

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  • 0

    You can only install equipment that conforms to a BS, BS EN or some other Harmonised Standard.

    If you want to install something else you can do it as a Departure but it has to be no les safe than the requirements of BS 7671. 

    JP

  • 0 in reply to John Peckham
    John Peckham said:
    You can only install equipment that conforms to a BS, BS EN or some other Harmonised Standard.

    Just a thought ...

    What is installed in e.g. the USA embassy? Presumably, by convention, the USA will be given discretion to fit it out as they see fit. Easy enough to get the voltage down, less easy to change the frequency.

    Then how about the RAF bases, e.g. Mildenhall, which host USAF units?

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  • 0 in reply to John Peckham
    John Peckham said:
    You can only install equipment that conforms to a BS, BS EN or some other Harmonised Standard.

    Just a thought ...

    What is installed in e.g. the USA embassy? Presumably, by convention, the USA will be given discretion to fit it out as they see fit. Easy enough to get the voltage down, less easy to change the frequency.

    Then how about the RAF bases, e.g. Mildenhall, which host USAF units?

Children
  • 0 in reply to Chris Pearson

    Embassies, foreign air bases and such places are, in parts, wired to US standards, as are the parts of labs such as that described by the OP where equipment intended for the US market is designed, developed or tested. Similar specialist configurations are also needed where for example equipment to go inside Aeroplanes (110V 400Hz and some very funny connectors) are designed, developed or tested.

    That does not mean that the conventional 230V 50Hz parts of those sites are not broadly '7671 complaint of course, nor that the bits that are not, are in some way made deliberately dangerous.

    As I keep pointing out from time to time, the UK's wiring regs are not the only ones on the planet, and there are a number of corner circumstances where they are not really applicable ;-) 

    Regards Mike.

    Addendum

    This might amuse you Chris, sites in the UK run by the European Space Agency are carefully excepted from several bits of legislation. 

    https://www.legislation.gov.uk/uksi/1978/1105/made 

    "6.—(1) The Agency shall have immunity from suit and legal process ..." sounds pretty sweeping, even with the exception for motoring offences.. 

    Indeed its a lot more general than https://www.legislation.gov.uk/ukpga/1964/81/2020-12-31 The diplomatic privileges act 1964 as amended.

    There is an ESA site  up the road a bit from us, among other things they use a lot of SY cable ;-) 

  • 0 in reply to Chris Pearson

    Morning Chris

    I have been to both RAF Mildenhall and Lakenheath which are USAF bases. I was more interested in their aircraft at the time but noted the electrical installation on one of the bases, cant remember which one, had US plugs and sockets.

    As for embassies, I have only been in side one, when you step of the pavement you leave the UK and enter a foreign country. I was there to look at the electrical installation and was followed around by  a couple of security people and an English speaking woman who was constantly shouting at them. 

    JP

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